c语言下的hashmap实现

参见文章

1.hashmap.h

/**
 * hashmap.h
 */
#ifndef _HASHMAP_H_INCLUDED
#define _HASHMAP_H_INCLUDED

#if defined(__cplusplus)
extern "C" {
#endif

#define HMAP_E_KEYUSED  (-5)     /* Key already existed */
#define HMAP_E_OUTMEM   (-4)     /* Out of Memory */
#define HMAP_E_NOTFOUND (-3)     /* No such element */
#define HMAP_E_OVERFLOW (-2)     /* Hashmap is full */
#define HMAP_E_FAIL     (-1)     /* Hashmap api fail */
#define HMAP_S_OK       (0)      /* Success */

/**
 * void_ptr is a pointer. This allows you to put arbitrary structures in the hashmap.
 */
typedef void* void_ptr;

/**
 * hmap_t is a pointer to an internally maintained data structure.
 * Clients of this package do not need to know how hashmaps are
 * represented. They see and manipulate only hmap_t's.
 */
typedef void_ptr hmap_t;

/**
 * hmap_callback_func is a pointer to a function that can take two void_ptr arguments
 * and return an integer. Returns status code..
 */
typedef int (*hmap_callback_func)(void_ptr, void_ptr);

/**
 * prototype for map element type
 */
typedef struct _hmap_pair_t {
	char *key;
	void_ptr data;
} hmap_pair_t;

/**
 * Return an empty hashmap. Returns NULL if empty.
 */
extern hmap_t hashmap_create();

/**
 * Iteratively call fn with argument (value, arg) for each element data
 * in the hashmap. The function returns anything other than HMAP_S_OK
 * the traversal is terminated. fn must not modify any hashmap functions.
 */
extern int hashmap_iterate(hmap_t in, hmap_callback_func fnIterValue,
		void_ptr arg);

/**
  * Add an element to the hashmap.
  * Return HMAP_S_OK, HMAP_E_KEYUSED or HMAP_E_OUTMEM.
  */
extern int hashmap_put(hmap_t in, char* key, void_ptr elem);

/**
 * Get an element from the hashmap. Return HMAP_S_OK or HMAP_E_NOTFOUND.
 */
extern int hashmap_get(hmap_t in, const char* key, void_ptr *elem);

/**
 * Remove an element from the hashmap. Return HMAP_S_OK or HMAP_E_NOTFOUND.
 */
extern int hashmap_remove(hmap_t in, char* key, void_ptr *outValue);

/**
 * Free the hashmap
 */
extern void hashmap_destroy(hmap_t in, hmap_callback_func fnFreeValue,
		void_ptr arg);

/**
 * Get the current size of a hashmap
 */
extern int hashmap_size(hmap_t in);

#if defined(__cplusplus)
}
#endif

#endif /* _HASHMAP_H_INCLUDED */

2.hashmap.c

/**
 * hashmap.c
 *   Generic hash map implementation.
 */
#include "hashMap.h"

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#define HMAP_INITIAL_SIZE (256)
#define HMAP_CHAIN_LENGTH (8)

typedef enum _hashmap_use_state {
	hashmap_unused_0 = 0, hashmap_used_1 = 1
} hashmap_use_state;

/* A element to keep keys and values */
typedef struct _hashmap_elem_t {
	char *key; /* pointer to actual key storage */
	hashmap_use_state used; /* unused_0, used_1 */
	void_ptr data; /* pointer to value memory allocated by callee */
} hashmap_elem_t;

/* A hashmap has maximum size and current size, as well as the elems to hold */
typedef struct _hashmap_map_t {
	int table_size;
	int size;
	hashmap_elem_t *elems;
} hashmap_map_t;

/**
 * The implementation here was originally done by Gary S. Brown.
 * I have borrowed the tables directly, and made some minor changes.
 *
 * COPYRIGHT (C) 1986 Gary S. Brown.
 *   You may use this program, or code or tables extracted from it,
 *   as desired without restriction.
 */
static unsigned long crc32_tab[] = { 0x00000000L, 0x77073096L, 0xee0e612cL,
		0x990951baL, 0x076dc419L, 0x706af48fL, 0xe963a535L, 0x9e6495a3L,
		0x0edb8832L, 0x79dcb8a4L, 0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL,
		0x7eb17cbdL, 0xe7b82d07L, 0x90bf1d91L, 0x1db71064L, 0x6ab020f2L,
		0xf3b97148L, 0x84be41deL, 0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L,
		0x83d385c7L, 0x136c9856L, 0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL,
		0x14015c4fL, 0x63066cd9L, 0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L,
		0x4c69105eL, 0xd56041e4L, 0xa2677172L, 0x3c03e4d1L, 0x4b04d447L,
		0xd20d85fdL, 0xa50ab56bL, 0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L,
		0xacbcf940L, 0x32d86ce3L, 0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L,
		0x26d930acL, 0x51de003aL, 0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L,
		0x56b3c423L, 0xcfba9599L, 0xb8bda50fL, 0x2802b89eL, 0x5f058808L,
		0xc60cd9b2L, 0xb10be924L, 0x2f6f7c87L, 0x58684c11L, 0xc1611dabL,
		0xb6662d3dL, 0x76dc4190L, 0x01db7106L, 0x98d220bcL, 0xefd5102aL,
		0x71b18589L, 0x06b6b51fL, 0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L,
		0x0f00f934L, 0x9609a88eL, 0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL,
		0x91646c97L, 0xe6635c01L, 0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L,
		0xf262004eL, 0x6c0695edL, 0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L,
		0x65b0d9c6L, 0x12b7e950L, 0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL,
		0x15da2d49L, 0x8cd37cf3L, 0xfbd44c65L, 0x4db26158L, 0x3ab551ceL,
		0xa3bc0074L, 0xd4bb30e2L, 0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL,
		0xd3d6f4fbL, 0x4369e96aL, 0x346ed9fcL, 0xad678846L, 0xda60b8d0L,
		0x44042d73L, 0x33031de5L, 0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL,
		0x270241aaL, 0xbe0b1010L, 0xc90c2086L, 0x5768b525L, 0x206f85b3L,
		0xb966d409L, 0xce61e49fL, 0x5edef90eL, 0x29d9c998L, 0xb0d09822L,
		0xc7d7a8b4L, 0x59b33d17L, 0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL,
		0xedb88320L, 0x9abfb3b6L, 0x03b6e20cL, 0x74b1d29aL, 0xead54739L,
		0x9dd277afL, 0x04db2615L, 0x73dc1683L, 0xe3630b12L, 0x94643b84L,
		0x0d6d6a3eL, 0x7a6a5aa8L, 0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L,
		0x7d079eb1L, 0xf00f9344L, 0x8708a3d2L, 0x1e01f268L, 0x6906c2feL,
		0xf762575dL, 0x806567cbL, 0x196c3671L, 0x6e6b06e7L, 0xfed41b76L,
		0x89d32be0L, 0x10da7a5aL, 0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L,
		0x17b7be43L, 0x60b08ed5L, 0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L,
		0x4fdff252L, 0xd1bb67f1L, 0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL,
		0xd80d2bdaL, 0xaf0a1b4cL, 0x36034af6L, 0x41047a60L, 0xdf60efc3L,
		0xa867df55L, 0x316e8eefL, 0x4669be79L, 0xcb61b38cL, 0xbc66831aL,
		0x256fd2a0L, 0x5268e236L, 0xcc0c7795L, 0xbb0b4703L, 0x220216b9L,
		0x5505262fL, 0xc5ba3bbeL, 0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L,
		0xc2d7ffa7L, 0xb5d0cf31L, 0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L,
		0xec63f226L, 0x756aa39cL, 0x026d930aL, 0x9c0906a9L, 0xeb0e363fL,
		0x72076785L, 0x05005713L, 0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL,
		0x0cb61b38L, 0x92d28e9bL, 0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L,
		0x86d3d2d4L, 0xf1d4e242L, 0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL,
		0xf6b9265bL, 0x6fb077e1L, 0x18b74777L, 0x88085ae6L, 0xff0f6a70L,
		0x66063bcaL, 0x11010b5cL, 0x8f659effL, 0xf862ae69L, 0x616bffd3L,
		0x166ccf45L, 0xa00ae278L, 0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L,
		0xa7672661L, 0xd06016f7L, 0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL,
		0xd9d65adcL, 0x40df0b66L, 0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L,
		0x47b2cf7fL, 0x30b5ffe9L, 0xbdbdf21cL, 0xcabac28aL, 0x53b39330L,
		0x24b4a3a6L, 0xbad03605L, 0xcdd70693L, 0x54de5729L, 0x23d967bfL,
		0xb3667a2eL, 0xc4614ab8L, 0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L,
		0xc30c8ea1L, 0x5a05df1bL, 0x2d02ef8dL };

/**
 * Return a 32-bit CRC of the contents of the buffer.
 */
static unsigned long crc32(const unsigned char *s, unsigned int len) {
	unsigned int i;
	unsigned long crc32val = 0;
	for (i = 0; i < len; i++) {
		crc32val = crc32_tab[(crc32val ^ s[i]) & 0xff] ^ (crc32val >> 8);
	}
	return crc32val;
}

/**
 * Hashing function for a string
 */
static unsigned int _find_hash_index(hashmap_map_t * m, const char* keystring) {
	unsigned long key = crc32(keystring, strlen(keystring));

	/* Robert Jenkins' 32 bit Mix Function */
	key += (key << 12);
	key ^= (key >> 22);
	key += (key << 4);
	key ^= (key >> 9);
	key += (key << 10);
	key ^= (key >> 2);
	key += (key << 7);
	key ^= (key >> 12);

	/* Knuth's Multiplicative Method */
	key = (key >> 3) * 0x9E3779B1;

	return key % m->table_size;
}

/**
 * Return the integer of the location in data to store the point to the item,
 *   or HMAP_E_OVERFLOW.
 */
static int _hashmap_hash(hmap_t in, char* key) {
	int curr;
	int i;
	hashmap_elem_t *elem;
	hashmap_map_t *m = (hashmap_map_t *) in;

	/* If full, return immediately */
	if (m->size >= (m->table_size / 2)) {
		return HMAP_E_OVERFLOW;
	}

	/* Find the best index */
	curr = _find_hash_index(m, key);

	/* Linear probing */
	for (i = 0; i < HMAP_CHAIN_LENGTH; i++) {
		elem = m->elems + curr;
		if (elem->used == hashmap_unused_0) {
			return curr;
		}

		if (elem->used == hashmap_used_1 && (!strcmp(elem->key, key))) {
			return curr;
		}

		curr = (curr + 1) % m->table_size;
	}
	return HMAP_E_OVERFLOW;
}

/**
 * Doubles the size of the hashmap, and rehashes all the elements
 */
static int _hashmap_rehash(hmap_t in) {
	int i;
	int old_size;
	hashmap_elem_t *curr;
	hashmap_elem_t *elem;

	/* Setup the new elements */
	hashmap_map_t *m = (hashmap_map_t *) in;
	hashmap_elem_t *temp = (hashmap_elem_t *) calloc(2 * m->table_size,
			sizeof(hashmap_elem_t));
	if (!temp) {
		return HMAP_E_OUTMEM;
	}

	/* Update the array */
	curr = m->elems;
	m->elems = temp;

	/* Update the size */
	old_size = m->table_size;
	m->table_size = 2 * m->table_size;
	m->size = 0;

	/* Rehash the elements */
	for (i = 0; i < old_size; i++) {
		int status;
		elem = curr + i;
		if (elem->used == hashmap_unused_0) {
			continue;
		}
		status = hashmap_put(m, elem->key, elem->data);
		if (status != HMAP_S_OK) {
			return status;
		}
	}

	free(curr);
	return HMAP_S_OK;
}

/**
 * Create an empty hashmap
 */
hmap_t hashmap_create() {
	hashmap_map_t* m = (hashmap_map_t*) malloc(sizeof(hashmap_map_t));
	if (!m) {
		exit(HMAP_E_OUTMEM);
	}

	m->elems = (hashmap_elem_t*) calloc(HMAP_INITIAL_SIZE,
			sizeof(hashmap_elem_t));
	if (!m->elems) {
		free(m);
		exit(HMAP_E_OUTMEM);
	}

	m->table_size = HMAP_INITIAL_SIZE;
	m->size = 0;

	return m;
}

/**
 * Add a pair of key-value to the hashmap
 */
int hashmap_put(hmap_t in, char* key, void_ptr value) {
	int index;
	hashmap_map_t *m;
	hashmap_elem_t *elem;

	m = (hashmap_map_t *) in;

	/* Find a place to put our value */
	index = _hashmap_hash(in, key);
	while (index == HMAP_E_OVERFLOW) {
		if (_hashmap_rehash(in) == HMAP_E_OUTMEM) {
			return HMAP_E_OUTMEM;
		}
		index = _hashmap_hash(in, key);
	}

	/* Set the elems */
	elem = m->elems + index;
	if (elem->used == hashmap_used_1) {
		/* Find a repeated key */
		return HMAP_E_KEYUSED;
	}
	elem->data = value;
	elem->key = key; /* only set to a reference */
	elem->used = hashmap_used_1;
	m->size++;

	return HMAP_S_OK;
}

/**
 * Get your pointer out of the hashmap with a key
 */
int hashmap_get(hmap_t in, const char* key, void_ptr *value) {
	int curr;
	int i;
	hashmap_map_t *m;
	hashmap_elem_t *elem;

	m = (hashmap_map_t *) in;

	/* Find element location */
	curr = _find_hash_index(m, key);

	/* Linear probing, if necessary */
	for (i = 0; i < HMAP_CHAIN_LENGTH; i++) {
		elem = m->elems + curr;
		if (elem->used == hashmap_used_1) {
			if (!strcmp(elem->key, key)) {
				*value = (elem->data);
				return HMAP_S_OK;
			}
		}
		curr = (curr + 1) % m->table_size;
	}

	*value = NULL;
	return HMAP_E_NOTFOUND;
}

/**
 * Iterate the function parameter over each element in the hashmap. The
 * additional void_ptr argument is passed to the function as its first
 * argument and the hashmap element is the second.
 */
int hashmap_iterate(hmap_t in, hmap_callback_func fnIterValue, void_ptr arg) {
	int i;
	hashmap_elem_t *elem;
	hashmap_map_t *m = (hashmap_map_t*) in;

	if (hashmap_size(m) <= 0) {
		return HMAP_E_NOTFOUND;
	}

	for (i = 0; i < m->table_size; i++) {
		elem = m->elems + i;
		if (elem->used == hashmap_used_1) {
			int status = fnIterValue(elem->data, arg);
			if (status != HMAP_S_OK) {
				return status;
			}
		}
	}
	return HMAP_S_OK;
}

/**
 * Remove an element with that key from the map
 */
int hashmap_remove(hmap_t in, char* key, void_ptr *outValue) {
	int i, curr;
	hashmap_map_t* m;
	hashmap_elem_t *elem;

	/* Cast the hashmap */
	m = (hashmap_map_t *) in;

	if (outValue) {
		*outValue = NULL;
	}

	/* Find key */
	curr = _find_hash_index(m, key);

	/* Linear probing, if necessary */
	for (i = 0; i < HMAP_CHAIN_LENGTH; i++) {
		elem = m->elems + curr;
		if (elem->used == hashmap_used_1) {
			if (!strcmp(elem->key, key)) {
				/* Blank out the fields */
				elem->used = hashmap_unused_0;
				elem->key = NULL;
				if (outValue) {
					*outValue = elem->data;
				}
				elem->data = NULL;

				/* Reduce the size */
				m->size--;
				return HMAP_S_OK;
			}
		}
		curr = (curr + 1) % m->table_size;
	}
	/* Data not found */
	return HMAP_E_NOTFOUND;
}

/**
 * Deallocate the hashmap
 */
void hashmap_destroy(hmap_t in, hmap_callback_func fnFreeValue, void_ptr arg) {
	hashmap_elem_t *elem;
	void_ptr data;
	hashmap_map_t* m = (hashmap_map_t*) in;

	while (m->table_size-- > 0) {
		elem = m->elems + (m->table_size);
		if (elem->used == hashmap_used_1) {
			elem->used = hashmap_unused_0;
			elem->key = NULL;
			data = elem->data;
			elem->data = NULL;

			if (fnFreeValue) {
				fnFreeValue(data, arg);
			}
		}
	}

	free(m->elems);
	free(m);
}

/**
 * Return the length of the hashmap
 */
int hashmap_size(hmap_t in) {
	hashmap_map_t* m = (hashmap_map_t *) in;
	if (m) {
		return m->size;
	} else {
		return 0;
	}
}